Sturgeon said her pro-independence Scottish National Party (SNP) would set out a timescale for a referendum in its manifesto ahead of regional elections next year.

"Our manifesto will set out what we consider are the circumstances and the timescale on which a second referendum might be appropriate," Sturgeon told the Press Association news agency.

The manifesto is due to be unveiled at the SNP's annual conference next month.

The party, which won 56 of Scotland's 59 seats in May's general election, pushed for a vote last year in which Scots voted by a margin of 55 percent to 45 percent against independence.

Sturgeon said it would be up to Scots to vote for or against the party manifesto and the referendum could be held "in five years or 10 years".

A poll by Ipsos Mori for Scottish television channel STV showed 55 per cent of voters in Scotland would back independence if there was another referendum.

"It doesn't surprise me in the slightest that support for independence has risen in the past year," Sturgeon said.

She said Conservative Prime Minister David Cameron's government had reneged on a promise to grant Scotland sweeping new powers and had pursued harsh budget austerity policies.

Sturgeon said that pressure for a vote would also grow because of "scaremongering" about Britain's membership of the European Union ahead of an in-out referendum which Cameron is planning to hold by 2017 at the latest.